ES2499466T3 - Safety element with parallax effect - Google Patents

Abstract

Security article (10), in particular a security document, comprising a security element (1) comprising an optical system, comprising: - a transparent or translucent substrate (2), - on the side of a first face (2a, 2b) of the substrate (2) a combined image (I) comprising a plurality of overlapped encoded images (I1, ..., IN), - on the side of a second face (2a, 2b) of the substrate ( 2), opposite the first one, a revelation frame (4) superimposed on the combined image (I), which allows the encoded images (I1, ... IN) to be observed during a change of the observation direction of the security element (1) in relation to the optical system, characterized in that the encoded images (I1 ... IN) are observable on the side of the first face and on the side of the second face of the substrate (2).

Description

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DESCRIPTION

Security element with parallax effect.

The present invention relates to the field of security elements that serve for the authentication and / or identification of various articles, documents or objects.

Background

In order to prevent imitations or falsifications and in order to increase the level of security, it is known to use security elements applied on the surface or introduced in bulk or in a window (s) in a security article, in particular a security document or another object, for example a label, a packaging, in particular for medicines, food, cosmetics, electronic parts or loose parts.

The security article can be chosen, in particular, from a means of payment, such as a banknote, a check or a restaurant ticket, an identity document such as an identity card, a visa, a passport or a driving license, a lottery ticket, a transport certificate or also a ticket for demonstrations.

The revelation of animated images by a parallax effect has been known for a large number of years.

Several patents based on this principle have been filed, for example US Patents 5,098,302, US 5,525,383 and US 6,286,873.

Processes for creating movement illusions are known, such as those described in US 5,901,484 and US 6,286,873, which use a carrier supporting several encoded images, corresponding, for example, to the decomposition of the movement of an object or an animal, and a transparent film carrying a network of parallel strokes, placed on the support. A relative movement between the encoded images and the network of parallel strokes allows to create the illusion of a movement.

US 6,286,873 teaches the possibility of observing encoded images on each side of an optical system comprising a revelation frame and a combined image, located on either side of a substrate. US 6,286,873 does not disclose a security article.

Various optical systems are also known from US publications No. 3,241,429, US No. 3,154,872, US No. 4,645,301, US No. 4,892,336, WO 94/27254, US No. 6,856,462, US 2005/184504 , US 5,708,871, WO 2005/052650, WO 2005/058610, US 2005/150964 and WO 2007/020048.

It is known to make security elements with lenticular networks associated with specific impressions in order to produce movement effects. SECURENCY sells them under the MOTION® brand.

US 2007/0279697 discloses a security element comprising an optical system that allows a litmus effect to be produced.

Document DE 10 2006 061905 discloses a security element according to the preamble of claim 1 with a transparent substrate, a plurality of embedded encoded images and a revelation frame superimposed on the encoded images, the encoded images being observable from two sides opposite of the substrate. However, the integration of said security element in an article or the observation of the images of the article from two opposite faces of the substrate integrated in the article are not mentioned in this document DE 10 2006 061905.

Summary

There is a need to benefit from security elements that comprise an optical system capable of producing optical effects that may contribute to the authentication or identification of an article or object, and whose eventual incorporation in an article or object such as paper is can perform relatively easily.

The object of the invention is, according to a first of its aspects, a security article, in particular a security document, comprising a security element that includes an optical system, comprising:

-a transparent or translucent substrate,

- on the side of a first face of the substrate a combined image comprising a plurality of embedded coded images,

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- on the side of a second face of the substrate, opposite the first, a revelation frame superimposed on the combined image, which allows the encoded images to be observed during a change of the observation direction of the security element with respect to the optical system,

the encoded images being observable on the side of the first side and on the side of the second side of the substrate.

The combined image may comprise at least two overlapped encoded images. Preferably, it comprises at least three overlapped encoded images in order to accentuate the visual animation effect during successive observations of the encoded images by changing the observation direction of the security element in relation to the optical system.

The revelation of the encoded images can be done by parallax effect.

The invention offers new possibilities to authenticate and / or identify an article or object that carries the security element, for example a security document.

The user, by varying the inclination of the optical system, can cause a succession of images to appear, which allows, for example, to create an animation effect.

The revelation plot may allow the human eye to visualize a different encoded image at the same time, the observer's brain being able to reconstitute for example a movement or observe hidden information.

In the invention, the different images that the observer can see are different from images resulting from a phenomenon of spatial interference between two superimposed networks, in other words a litmus effect. Such an effect may result from a displaced orientation of the overlapping networks at a specific non-zero angle and may disappear when the networks are exactly overlapping or are displaced at a different angle from the specific angle. The invention preferably seeks to avoid said effect. The step of observing one encoded image to another when the angle of observation varies can be done without progressive transition.

The security element can provide anti-photocopy security. In particular, the fineness of the frame of the revelation and / or of the combined image, in particular less than 200 µm, can prevent photocopy reproduction and also ensure protection against the use of scanners.

The resolution of the combined image and / or the revelation plot may be directly related to the thickness of the substrate. It may be greater than or equal to 800 dpi, preferably greater than 2000 dpi and, more preferably, greater than 3000 dpi.

The revelation plot and / or the combined image can be as such, homogeneous in appearance, with its fineness in mind. In particular, the revelation plot may appear to the naked eye as having an appearance, in particular a uniform color.

Having a revealing plot of homogeneous appearance at a glance can make the security article according to the invention pleasant and interesting for the consumer.

Authentication and / or identification of the article can be carried out indifferently by observing the front or back of the security article.

Indeed, since the revelation plot and the combined image are present respectively on either side of the substrate, the encoded images can be observed in reflection on the obverse side, which coincides, for example, with the plot side. of revelation, but also on the reverse side. When the security element is integrated in a security document, for example in windows, it can be advantageous to make both the front and back sides of the security element observable.

Advantageously, the security element may appear in a window of a security article.

The window can be formed by an absence of material, for example the local lack of paper, above or below the security element, the window being at least partially transparent or translucent on the side of the security element opposite to the absence of material. Thus, it may be possible to observe a first side of the security element on the side of the absence of material and a second side of the security element, opposite the first, on the side of the transparent or translucent area of the window.

The window may not include a lack of material. The window can be, for example, at least partially transparent or translucent on either side of the security element, the transparent or translucent areas being superimposed on each other in order to be able to observe the two opposite sides of the

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security element.

The window can also be an intern. The window may have absences of overlapping materials on either side of the security element. The two sides of the security element can thus be directly observable and not through transparent or translucent areas. The security element can be incorporated totally or partially in the window.

The article may also have a plurality of windows such as those described below. The windows can be all of them or not of the same type. The article may comprise a security element whose opposite sides are visible at the level of the windows, through transparent or translucent areas or directly by the absence of material.

Examples of realization of windows in security documents are described, for example, in GB 1 552 853 which discloses the creation of a window, in particular by transparentization, laser cutting, abrasion or mechanical incision, the document EP 0 229 645, which describes the creation with masks of a window on one side or on both sides of a bilayer paper, WO 2004/096482, which describes the creation of a window by laser cutting, the document CA 2 471 379, which describes the creation of a transparent window and the association with a security element, and WO 2008/006983, which describes the creation of a transparent window on a bilayer paper.

The security article may, in particular, be a security document comprising paper fibers.

In particular, the invention can make it possible to secure security articles, in particular security documents that include paper fibers, such as banknotes or passports, with security elements having a relatively small thickness. The use of a relatively thin substrate, for example of thickness less than or equal to 50 µm, preferably 30 µm, requires the use of printing or marking systems of a very important definition, which further increases the degree of security.

The encoded images may represent information hidden and revealed successively by changing the angle of observation of the optical system. The security element may be configured to allow the observation of the succession of several images when the observation direction changes, which is also called "animation effect". In the context of the invention, the term "animation" must be broadly understood. It can be several images of the same object, which represent different angles of view, in order to provide a 3D or relief effect, rather than a movement effect. The combined image may correspond to the decomposition of the movement of a motif, for example of a text, alphanumeric signs, ideograms, an object, a person and / or an animal. Encoded images (also more simply called overlapping images) can represent successive stages of the movement of a motif, for example of an object, a person and / or an animal.

The revelation plot can have an outline of any shape, for example circular, oval, star, polygonal, for example rectangular, square, hexagonal, pentagonal or rhombus, among others.

The outline of the revelation plot may represent, for example, a text, an alphanumeric signal, an ideogram, an object, a person and / or an animal.

The combined image and / or the revelation plot can be carried on the substrate by a printing process, for example offset, sweet size, laser, heliogravure or screen printing. For example, the combined image and / or the revelation pattern can be printed with color or non-color inks, visible to the naked eye, under ultraviolet (UV) and / or infrared (IR) light, opaque or luminescent, in particular fluorescent, thermochromes, photochromes, of interferential effect, in particular iridescent, or of optically variable effect according to the angle of observation (gonochromatic), comprising in particular liquid, metallic or not, magnetic or not crystals, among others. When a magnetic ink is used, the drawn motif may constitute a magnetic signature that allows a supplementary authentication of the substrate by detection of said signature. The combined image and / or the revelation plot may also comprise metallizations and / or demetallizations, for example aluminum. Metallizations and / or demetallizations can be used in order to avoid falsification by printing. Metallizations and / or demetallizations can also be used when the security element is incorporated into a security article, in particular when the security element is of the security thread type.

The combined image and / or the revelation frame can also be printed with liquid crystals, such that the encoded images are, for example, visible only through a polarizer.

The optical system can be carried by a patch and / or a sheet. The patch and / or the sheet may comprise metallizations and / or demetallizations, for example aluminum, or any type of printing. The optical system can also be carried by a security thread, incorporated in the surface, in the mass or in window (s) in the security article. The width of the safety thread is, for example, between 3 and 20 mm, approximately equal to, for example, 4 mm.

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The substrate of the optical system may comprise or consist of a thermoplastic material, for example a polyolefin, for example polyethylene (PE), polyvinylchloride (PVC), polyester, polyethylene terephthalate (PET), polycarbonate (PC), carbonate Polyester (PEC), polyethylene glycol terephthalate (PETG), acrylonitrile-butadiene styrene (ABS) or a light-collecting film, for example of the "waveguide" type, for example a polycarbonate-based luminescent film marketed by BAYER Low the name LISA®.

The substrate may comprise cellulosic fibers and, in particular, paper. In particular, said substrate can be a sufficiently translucent paper to allow revealing the encoded images, in particular a tracing paper.

The substrate can also be transparentized by applying a generally fatty composition that permanently transparentizes it, for example a composition made of oil and transparent mineral material, as described in US Patent No. 2,021,141, or, for example, a composition in the form of a wax combined with a solvent, as described in US Patent No. 1,479,437.

The substrate can also be transparentized by applying a hot transfer wax locally, as described in US Patent No. 5,118,526.

A fibrous layer comprising a hot melt material, for example polyethylene, can also be used for the substrate, as described in EP 0 203 499, which, under the local action of heat, will see its transparency vary.

Advantageously, the revelation plot and / or the combined image can each be made with at least two overlapping colors so that, on the reverse side, the encoded images are observed in a first color and, on the obverse side , in a second color.

The revelation plot and / or the combined image can be monochromatic or polychromatic. In particular, at least one encoded image of the combined image can be monochromatic or polychromatic. The embedded coded images can also be made at least in part with thermochromic and / or photochromic inks. In this way, only part of the encoded images can be observable, for example, in predefined lighting and / or temperature conditions.

The combined image and / or the revelation plot can be made with different colors. In this way, it may be possible to obtain a color animation effect while observing the encoded images.

The use of color to make the security element can make it possible to further secure an article that integrates said security element. Most printers use tetrachromia with the colors "black", "cyan", "magenta" and "yellow". A photocopier with a maximum resolution equal to 1200 dpi can reproduce a combined black image for which the width of a stroke of an encoded image is 21 µm or more. However, to reproduce the colors, in particular the colors different from black, cyan, magenta or yellow, this photocopier uses frames of cyan, magenta and yellow. The maximum effective resolution of this photocopier in reproduction of a combined image is thus estimated at approximately 1200/3 = 400 dpi. Such a resolution corresponds to a combined image for which the width of a stroke of an encoded image is 63 µm or more. The increase in the resolution of the plot and the combined image and / or the use of color can thus allow to increase the level of security of the security element.

For example, all overlapped encoded images of the combined image may have the same color and the disclosure pattern may have a different color. As a variant, the embedded coded images of the combined image may have different colors and the disclosure frame may have a different color than the imbricated coded images or similar to the color of at least one of the imbricated coded images. The revelation plot and / or the combined image may be opaque or not. In particular, the disclosure frame and / or the combined image may be at least partially translucent or transparent and, for example, may be colored or absorbent at a given wavelength, in the UV or IR domain.

The security element may also comprise two disclosure frames associated respectively with two combined images, the orientation of the bands of one of the disclosure frames being different from that of the other disclosure frame. When the bands are non-rectilinear, their orientation is defined by the general direction in which they extend.

The security element may comprise two revealing frames juxtaposed or not, superimposed or not, comprising bands that have different orientations or not. One of the disclosure frames may be totally or partially surrounded by the other disclosure frame. The eventual overlapping zone of the revelation frames can make a grid form appear when the bands of the revelation frames have different orientations.

The thickness of the substrate is, for example, between 10 µm and 1 mm, in particular between 6 µm and 1 mm,

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preferably between 6 µm and 300 µm, preferably between 10 and 100 µm, being, for example, between 30 µm and 50 µm.

It may also be less than 50 µm, in particular 25 µm. The period of the disclosure frame and / or the combined image is preferably less than or equal to the thickness of the substrate.

A security element with a resolution of the combined image and / or the revelation frame greater than or equal to 800 dpi, as well as with a substrate thickness and a relationship between the period of the revelation frame and / or the image combined and the thickness of the substrate as described above, can allow to obtain an animation visible to the naked eye, despite the fineness of the plot and the combined image, and strengthen the security of the device against photocopies and copies of this latest.

The number of embedded encoded images is, for example, between 2 and 15, in particular between 2 and 5, preferably being greater than or equal to 3. The distance between two constituent elements of the same encoded image may be between 2 µm and 1 mm, in particular between 10 µm and 1 mm, preferably being substantially equal to the period of the disclosure frame. The width of a constituent element of an encoded image is preferably less than or equal to 500 µm, better 100 µm. The width of an opacifying band of the revealing web is preferably less than or equal to the thickness of the substrate, in particular 1 mm.

The revealing frame may comprise opacifying bands with parallel edges, possibly non-rectilinear. The presence of opacifying bands of non-rectilinear edges can make the reproduction of the optical system by a counterfeiter more difficult.

The disclosure frame can be printed or made in another way, in particular by metallization or demetalization, as indicated above.

The security element may also comprise a revealing frame comprising at least a first fluorescent zone capable of emitting, in a predefined lighting condition, a visible light of a first color, and a combined image comprising at least a second fluorescent zone capable of emitting by fluorescence, in the condition of predefined lighting, a visible light of a second color, different from the first, being at least one of the first and second fluorescent zones, in particular the two, at least partially opaque, at least in the condition of predefined lighting, and at least partially overlapping the first and second fluorescent zones so that, in the condition of predefined lighting, a light that successively crosses the two fluorescent zones has a third different color of the first and second colors. In particular, the security element may use the principle described in international application WO 2006/051231. The predefined lighting condition may correspond in particular to ultraviolet illumination, in particular of wavelength close to the visible one, or to infrared illumination, depending on the fluorescent compounds used. At least one of the first and second fluorescent zones, in particular both, can be substantially colorless in white light.

The security element may comprise a plurality of optical systems associated with different observation directions. For example, the security element may comprise an alternation of optical systems associated with two respective perpendicular directions, in particular optical systems whose respective revealing frames have perpendicular orientations.

The security element may be totally or partially covered with an invisible material in "normal" lighting, that is, when it is illuminated by daylight or an artificial light source. This invisible material in normal lighting is, for example, a material visible under specific lighting, in particular a luminescent material, for example a fluorescent or phosphorescent material visible under UV or IR lighting.

As a variant, the material may comprise nematic liquid crystals visible on a reflective background (the weft and / or the image and / or the background being then reflective) with a polarizing filter, in particular circular.

The total or partial coverage of the security element by such invisible material in "normal" lighting can form a supplementary security in the form of a motif, for example of a word, acronym, code, symbol, image, alphanumeric character or ideogram.

As a variant, said invisible material in "normal" lighting does not cover the security element, but is arranged between the frame and the image, then being partially observable, but sufficiently.

The use of an invisible material in "normal" lighting can thus confer a second level supplementary security to the security element. Next, a second level security element is defined.

The security article may comprise a security element comprising a plurality of optical systems associated with different observation directions, a part of the optical systems being such that the associated encoded images are observable only from a first side of the security element and

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another part of the optical systems being such that the associated encoded images are observable only from a second side of the security element opposite to the first. As a variant, the encoded images associated with the optical systems can be observed from two sides of the security element.

The observation of the encoded images can also be facilitated and improved by the choice of a background on which the security element is placed or on which the security element or the security article comprising it is to be placed.

When the security element is incorporated in a window in an article, either in a through window or alternatively appearing on the side of a first face of the article and on the side of a second face of the article, for example opposite to the first, the bottom can be arranged alternately on either side of the security element so that the embedded images and / or the revelation plot are observable at the same time from the first side of the article and from the second side of the article.

The security element may thus comprise the background, the latter being positioned such that the revelation frame is between the background and the substrate or that the combined image is between the substrate and the background.

The fund may also be independent of the security element. For example, the user can place the security element or the security article near the bottom, better in contact with it, whether it is colored or not.

The bottom can be constituted by any substrate, preferably being flattened, for example a sheet of paper or cardboard.

The background can be arranged in such a way that the user can observe the side of the security element comprising the disclosure frame or the side comprising the combined image.

Observation in the presence of the background may allow the appearance of a contrast effect between the background, the combined image and the revelation plot. The contrast effect can be improved, in particular, during the use of a combined image, a revelation frame and a background of different colors.

The bottom may comprise at least one luminescent element, for example fluorescent and / or phosphorescent. The effect can be observed under a predefined lighting, for example UV or IR. The bottom may also comprise a metallic layer.

The contrast effect can also be obtained without the presence of the background, in particular by the simple fact of using a light source when the security element is observed in transmission on the side of the combined image or on the side of the revelation plot. Indeed, the light source can play the same role as a colored background and allow the appearance of a contrast effect by combining the different colors of the light source, the combined image and the revelation plot.

The combined image and the revelation plot may have the same color, and the background may be of a different color, being particularly more contrasted.

The security article may also comprise a perforation in which at least partially the security element is placed, the latter corresponding, for example, to the juxtaposition of two sub-elements, in particular in the form of sheets or patches, which respectively comprise a revelation plot and the corresponding combined image.

Sub-elements may at least partially cover the edges of the perforation, with or without thickness compensation.

The security article may also comprise a disclosure frame or a combined image made in the form of prints and a sub-element, in particular in the form of a sheet or patch, which covers at least partially the impressions formed, the sub-element comprising the combined image or the corresponding disclosure plot. Prints of the combined image can be made, for example, on the surface of the security article.

The or each sub-element may comprise a transparent or translucent substrate.

The or each sub-element, in particular the patch or the sheet, can be incorporated into the security article by gluing or by incorporation into the fibrous substrate of the article during its manufacture.

The optical system can comprise at least two combined images and a single frame that allows, during a change in the observation angle, to successively observe the imbricated images of the two combined images. The two images combined can be arranged so that a movement

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relative of an image combined to the other one is perceived by a user during a change in the observation direction of the security element in relation to the optical system.

The substrate may comprise at least two distinct layers and the optical system may comprise at least two combined images, one of them being arranged in front of an outer face of one of the layers of the substrate, in particular on it, and the another combined image arranged between the two layers.

The two layers of the substrate can have the same thickness. These two layers can be transparent.

Each combined image may comprise a plurality of embedded coded images.

Each combined image may comprise the same number of encoded images and / or each combined image may have the same resolution, in particular one of the resolution values mentioned above, and / or the distance between two constituent elements of the same encoded image of the same. First combined image may be equal to the distance between two constituent elements of the same encoded image of the second combined image.

The subject of the invention is also a method of authenticating a security article according to one of claims 1 to 13, which comprises the step of observing the security article by varying the observation direction of the optical system and drawing a conclusion. on the authenticity of the article or object associated with the security article based on the images observed. The observation can be carried out, for example, on the front and back sides of the substrate.

The article or object, or even security element, in particular in the form of a security thread, patch or sheet, may comprise one or more different security elements, such as those defined below.

In general, among the security elements some are detectable with the naked eye, in daylight or with artificial light, without the use of a particular device. These security elements comprise, for example, colored fibers or slabs, printed or metallic threads, totally or partially. These security elements are called first level.

Other types of safety elements are detectable only with the help of a relatively simple device, such as a lamp emitting in the ultraviolet (UV) or infrared (IR) domain. These security elements comprise, for example, fibers, planks, bands, threads or particles. These safety elements may be visible to the naked eye or not, being, for example, luminescent under the illumination of a Wood lamp emitting at a wavelength of 365 nm. These security elements are called second level.

Other types of security elements also need a more sophisticated detection apparatus for their detection. These security elements are capable, for example, of generating a specific signal when they are subjected, simultaneously or not, to one or several external excitation sources. Automatic signal detection allows the article to be authenticated, if necessary. These safety elements comprise, for example, tracers that are presented in the form of active materials, particles or fibers, capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are called third level.

The security elements present within the security article may have first, second and / or third level security features.

The invention can be better understood by reading the following description of non-limiting embodiments thereof, and by examining the attached drawing, in which:

- Figure 1 represents in section, schematically and partially, an example of an optical system made in accordance with an embodiment of the invention,

- Figure 2 represents, in front view, on an enlarged scale, an example of a revelation plot,

-Figure 3 illustrates the decomposition of the combined image into encoded images,

-Figure 4 illustrates the formation of an encoded image,

-Figure 5 represents a succession of coded images as can be seen when the angle of observation varies,

- Figures 6A to 6H represent other examples of disclosure frames,

- Figure 7 is a view similar to Figure 1, of a variant embodiment of an optical system,

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-Figure 8 illustrates the possibility of varying the inclination by deforming the substrate,

-Figure 9 represents a security element comprising several optical systems corresponding to different respective observation directions,

- Figures 10 and 11 represent two examples of security documents according to the invention,

- Figures 12A, 12B, 12C and 12D represent examples of security documents according to the invention,

- Figures 13A and 13B represent an example of a security document according to the invention, respectively after its photocopy and before its photocopy,

- Figures 14 to 16 illustrate variants of observation of security elements,

-Figure 17 illustrates a variant embodiment of the revelation plot and the combined image,

Figures 18 and 19 illustrate variants of embodiment of security articles according to the invention, and

-Figure 20 illustrates other safety items.

A security element 1 that can be incorporated into a security article according to the invention and which comprises a non-opaque substrate 2, for example perfectly transparent, having a first face 2a bearing a plurality of images is shown in FIG. encoded I1, I2, ..., In-built, presenting the constituent elements 3 of these images, for example in the form of continuous or discontinuous strokes, most often discontinuous. The set of encoded images I1, ..., In forms a combined image I, as can be seen in Figure 3.

The second face 2b of the substrate 2, opposite the first, has a revealing frame 4 (also called a decomposition filter) comprising opacifying bands 5 (or strokes).

The revelation frame 4 is composed of a periodic motif, in this case the opacifying band 5, of constant period p, as can be seen in Figure 2. The periodicity is observed parallel to the direction of the relative displacement X between the optical system and the observer, which allows observing the different encoded images.

The simplest embodiment of the disclosure frame 4 is a succession of opacifying bands 5 of constant width at regular intervals, as illustrated in Figure 2. The period p corresponds to the sum of the width of an opacifying band 5 and an interval transparent between two 5 consecutive opacifying bands. In the illustrated example, each of the opacifying bands 5 is oriented perpendicularly to the axis of relative displacement X.

The revelation frame 4 may comprise other motifs other than bands of constant width with straight and parallel edges, such as teeth or undulations, as illustrated respectively in Figures 6A and 6B.

If N is the total number of encoded images, a possible relationship between the period p of the disclosure frame, the width w of the transparent zone between two opacifying bands 5 of the frame 4 and the number N is:

N = (p / w).

The transparent intervals 8 of the disclosure frame 4 can, if desired, allow to reveal only one image at a time. An encoded image then corresponds to the parts of the combined image present in the transparent intervals of the frame for a given viewing angle. Each encoded image can be visible by displacing the observation of the width of a transparent interval 8.

All the constituent elements of the same encoded image are arranged, in the example described, with the same period p as opacifying bands of the revelation frame 4, along the X axis.

An example of forming a combined image I by adding a plurality of encoded images, for example four images encoded I1 to I4, is illustrated in Figure 3.

The embodiment of an encoded image Ii from an original image J to which the image of the revelation frame 4 is subtracted is illustrated in Figure 4.

Figure 5 shows the appearance of the different images I1 to I4, when the viewing angle α represented in Figure 1 changes in relation to the optical system. The animation corresponding to the

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encoded images can be revealed in reflection, on the side of the revelation plot and on the side of the combined image.

On the other hand, although a single disclosure frame serves to create the combined image, several different disclosure frames can be used to reveal the encoded images.

For example, as illustrated in Figures 6C to 6E, all disclosure frames that retain the same period and the same motif as the initial frame can be used, in the direction perpendicular to the translation, but with a transparent interval width different. This can allow viewing several encoded images at the same time, which can bring clarity to the animation, to the detriment of the definition.

Revelation frames also operate that have a multiple period of the period p of the initial frame, which is equivalent to artificially increasing the number N of encoded images to the detriment of the definition of the images, as illustrated in Figures 6F to 6G.

Obviously, various actions can be performed simultaneously on the period p and on the width of the transparent interval 8, as illustrated in Figure 6H.

In order to be able to visualize all the encoded images up to an inclination angle of approximately 45 °, the period p is preferably less than or equal to approximately the thickness e of the substrate, as shown in Figure 1.

A security thread generally has a maximum thickness of 50 µm, which corresponds to a period of less than or equal to 50 µm. In the case where four imbricated images are provided, the strokes 3 that make up the imbricated images will generally have a width less than or equal to 12.5 µm. The system that allows the combined image to be formed then has a minimum resolution of (2.54 x 10-2) / (12.5 x 10-6), that is, 2032 dots per inch (dpi or dpi).

The frame can then be presented in the form of a sequence of lines of 3 x 12.5 = 37.5 µm in width and separated by a distance of 12.5 µm.

For example, if a substrate of approximately 100 µm thickness e is used, the period p of the frame is less than 100 µm and the constituent elements in the form of strokes 3 that make up the encoded images are less than 33 µm, in the case of three images per animation.

A width of 12.5 µm corresponds to approximately 2000 dpi, which represents a limit for conventional printers that generally have a maximum definition of 600 dpi, or even 1200 dpi, which constitutes a security factor, in particular copy protection or antiphotocopy

Thus, it may be advantageous to have a substrate whose thickness is less than or equal to 30 µm, better 25 µm, for example between 20 and 30 µm, including 20 and 25 µm, limits included or excluded.

A sufficiently thin revelation frame allows to provide an anti-photocopy security and the existence of several encoded images that have details to be visualized according to different observation directions also creates a protection against the use of scanners.

On the other hand, since the human eye does not perceive the details below about 200 µm, a sufficiently thin revelation weave appears homogeneous in appearance, for example gray during the use of black opacifying bands. Despite the fineness of the revelation plot, the animation can be preserved, comprising encoded images of a scale greater than one millimeter, which contrast with the homogeneous aspect of the plot.

As previously stated, one might think that the resolution values mentioned above are too important to allow the observation of an optical effect, corroborating this impression due to the fact that the eye cannot distinguish the lines of the plot and sees it as a homogeneous flattening.

It can be considered that the resolution power of the human eye is one minute of arc, which corresponds to an observation distance of 30 cm, acceptable in the case of a security document, at a value of 2 x tg (1/120 ) x 3010-2 = 8710-6 m, that is 87 µm.

Despite the fineness of the plot and the combined image, the embedded images can be successively visible during an observation angle load.

Resolutions of more than 2000 dpi, even 3000 dpi, can make it possible to secure the device further.

Therefore, whatever the color or colors used for the revelation plot and / or the combined image, the

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Print definition can be accurate enough to make the mixture of colors appear homogeneous.

By way of example, an example of security document 10 according to the invention comprising a plurality of security elements 1 is illustrated in very enlarged figures 13A and 13B.

Figure 13A represents the observation of the security document 10 after its photocopy, and Figure 13B represents the observation of the document 10 before its photocopy. As can be seen, the invention provides high anti-photocopy security. In addition, the revelation plot can be thin enough to provide a homogeneous coloring effect during observation, contrary to what is seen in Figure 13B, which is greatly enlarged.

Since the optical system can operate in transmitted or reflected light, it can be used for windows or wires introduced into windows, for example on a banknote.

It is not necessary to signal the revelation frame with respect to the combined image in the direction of the relative displacement X. However, depending on the pattern of the plot, signaling in the direction perpendicular to this displacement may be necessary. For example, for a linear disclosure frame such as that illustrated in Figure 2, no signaling is necessary; on the contrary, a more or less precise signaling may be desirable for a wavy frame, depending on the amplitude and frequency of the undulations. The invention thus offers a possibility of modular security depending on the protection demanded and the difficulty of realization.

The combined image I and / or the revelation frame 4 can be formed by printing, demetalization, laser marking, lithography or any other technique that allows to fix or make an image appear.

To improve safety, liquid crystal inks can be used, for example to print the combined image I. The animation, to reveal itself, may also require, in addition to the decomposition pattern, the use of a polarizing filter, which may be present in the document or substrate, or not.

For the security elements formed by a thread inserted in a window (s) in a security document, the combined image I can be obtained by microfotolithography of the thread and the revelation pattern 4 can be made thanks to a UV offset printing made in a second time, during printing of the document.

The disclosure frame 4 may be associated, if necessary, with a print design of the document.

The motif of the disclosure frame 4 can be printed other than in overlapping with the combined image I, on the document, on the same scale or on a different scale.

The printing of the disclosure frame 4 can overflow from the security element 1 and extend over the security document 10, as illustrated in Figure 10.

It is possible to use several colors, for example a first color for the revelation pattern 4 and one or several different colors for the combined image I, for example as many different colors as there are encoded images.

It is also possible to superimpose two colors on the revelation frame 4 and the combined image I, as illustrated in Figure 7, which allows to have the animation of a color in case of observation of the optical system on the side of the frame and of another color in case of observation of the optical system on the side of the combined image.

This double coloring can be done by demetalization or photolithography, for example.

In Fig. 7, the revelation frame 4 comprises superimposed opacifying bands 5a and 5b, respectively of a first color C1 and a second color C2, the opacifying bands 5a of color C1 being exterior. The elements 3 of the combined image I are printed respectively with the two colors C1 and C2 superimposed, the elements of color C2 being exterior. Thus, the order of superposition of the colors can be the same on each side of the substrate 2.

One possibility for varying the observation direction of the optical system may be to deform the substrate, for example with respect to a folding axis, as illustrated in Figure 8.

Several optical systems, which have, for example, the shape of small squares or rectangles of a few millimeters on the side, may be present on the same security thread 20, as illustrated in Figures 9 and

eleven.

The rotation of a quarter turn of an optical system 1 in two can allow obtaining a thread that produces animations from relative displacements of the thread in the two main axes Y1 and Y2 with respect to the observer.

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When the security element is a thread integrated in window (s), as illustrated in Figures 12A and 12B, the document 10 may comprise at least two windows 31 and 32 which allow each of the faces of the thread to be observed respectively in reflection.

The substrate of the document may comprise at the level of windows 31 and 32 some absence of material and transparent areas 35 and 36 that allow the observation of the images encoded by the two sides of the security document.

The encoded images are observable through the disclosure frame 4 on the side of the window 31 and with the disclosure frame as background, on the side of the window 32.

The document 10 may also comprise a through window 31, as shown in Figure 12D, the security element 1 being at least partially located in this through window. In this way, it is possible to observe the encoded images at the same time on the obverse side and on the reverse side of the security document 10.

The security element 1 in the form of a security thread can also be incorporated in a security document 10 which has an alternation of windows 31 and 32 on the front side and on the reverse side, as illustrated in Figure 12C. It is thus possible to observe the encoded images at the same time on the obverse side and on the reverse side of the security document 10 at the level of the windows 31 and 32 and, in particular, due to the presence of the absence of material and the areas transparent 35 and 36.

In figures 14 and 16 there are illustrated variants of observation of security elements 1 that can be incorporated into a security article according to the invention. For simplicity, the security article has not been represented.

The observation of the security element 1 can be carried out thanks to the use of a bottom 30 on which the article comprising the security element 1 would be placed. In particular, the face 2b of the security element 1 comprising the disclosure frame 4 may be in contact with the bottom 30, as illustrated in Figure 14. As a variant, the face 2a of the security element 1 comprising the combined image I may be in contact with the bottom 30, as illustrated in the figure fifteen.

In these exemplary embodiments, the disclosure frame 4 is black, the combined image I is red and the background 30 is green. In this way, the observation of the security element 1 generates an important contrast effect resulting in particular from the choice of the colors of the revelation plot, the combined image and the background.

In the example of figure 14, the user can thus observe a black revelation frame 4 and a red spiral in contrast to the black color of the revelation frame and the green color of the background.

In the example of figure 15, the user can thus observe a revelation frame that appears as a mixture of red and black, the red color of the encoded images may be formed by pixels, and a red spiral in contrast to the green color of the background and the mixture of the black and red colors of the revelation plot.

The contrast effect obtained can also result from the simple observation in transvision of the security element 1 in the vicinity of a light source 31, for example sunlight, as illustrated in Figure 16.

A variant embodiment of a revealing frame 4 and of a combined image I that can be used in a security element 1 of a security article 10 according to the invention is shown in FIG.

In particular, this exemplary embodiment illustrates the possibility of making a revelation frame 4 and a combined image I such that the encoded images can be observable in the two main directions of inclination of the security element 1, in particular in the sense of width and length.

The revelation frame 4 can thus result from the superposition of two frames 4a and 4b which have bands extending along perpendicular axes, as can be seen in Figure 17. In the same way, the combined image I can result from the superimposition of combined images Ia and Ib corresponding respectively to the combined images associated with frames 4a and 4b.

The animation effect obtained can thus be observable in at least two directions of inclination of the security element 1.

An example of a security article 10 is shown in FIG. 18, comprising a perforation 40 in which at least two sub-elements are placed, in particular in the form of sheets or patches 41 and

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42, to form a security element 1 according to the invention.

Sub-element 41 comprises, for example, a disclosure frame 4 and sub-element 42 comprises, for example, the corresponding combined image I.

5 Sub-elements 41 and 42 can be superimposed at least partially to the edges of the perforation 40 with or without a thickness compensation.

Sub-elements 41 and 42 may be at least partially transparent or translucent.

10 The observation of the encoded images can be carried out by observation in reflection or in transvision, for example with the help of a light source located behind the article during observation.

In the variant illustrated in Figure 19, the security article 10 comprises a combined image I made in

15 impressions form. The prints are made, for example, on the surface of the security article 10. In addition, a sub-element, in particular in the form of a sheet or patch 43, is placed on the prints constituting the combined image I, the sub-element 43 comprising the revealing frame 4 corresponding, for example made on the surface of the sub-element 43.

20 Security article 10 may be opaque or not. The security article 10 may be at least partially transparent or translucent to allow observation of the encoded images, in particular on the side of the combined image I.

In the examples of Figures 18 and 19, the frames of revelations 4 and / or the combined images I could be made differently, for example being incorporated or located above or below the sub-elements 41, 42 and 43.

In the example of Figure 20, a security element 1 differs from that of Figure 1 in that it comprises two non-opaque substrate layers 2 for example perfectly transparent and two combined images I and I ’. The two layers of substrate in this case have the same thickness, for example 25 µm.

The first combined image I is arranged in front of the face 2b of the security element and represents, for example, a motif such as a cloud.

35 The second combined image I ’is arranged between the two layers of substrate 2 and represents in the example considered a motif such as a horse.

The period p of the revelation frame in the example considered is equal to the thickness of a substrate layer, that is to say 25 µm.

40 The embedded images Ii and I'i, which respectively form the first and second images combined, are arranged in the same manner in the example of Figure 20, whereby, during a change of observation angle from the face 2a of the security element, the motive represented by the second combined image I 'will move twice as slowly as the motive represented by the first combined image I, given

45 that will have been visualized by the eye twice as much of imbricated images I’i than of imbricated images Ii. This example shows the possibility with the invention of obtaining a movement effect between the motifs represented in the imbricated images. An effect of this type, which can also be described as "depth effect", is, for example, similar to that sought by "differential scrolling" of the first video games.

50 The example of Figure 20 can be obtained by assembly, in particular by gluing, of the different substrate layers 2. According to another method, the example of Figure 20 is obtained from a monolayer laser-marking substrate, in the that at least the combined image I is formed in the substrate by exposure to a laser radiation. The combined image I ’and / or the revelation plot are printed or marked in particular by laser radiation.

The use of the laser allows marking said laser-marking substrate to the desired depth, and also marking said substrate at least two different depths (thicknesses), for example to form on a monolayer substrate at least two of the elements between the revelation plot and the combined images.

The invention is not limited to the examples illustrated. The security element can be carried out with other first, second or third level securities, for example.

The expression "comprising a" should be understood as a synonym for "comprising at least one".

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Claims (14)

5 fifteen 25 35 Four. Five 55 65 E10740387 05-09-2014 1. Security article (10), in particular a security document, comprising a security element (1) comprising an optical system, comprising: -a transparent or translucent substrate (2), - on the side of a first face (2a, 2b) of the substrate (2) a combined image (I) comprising a plurality of imbricated encoded images (I1, ..., IN), - on the side of a second face (2a, 2b) of the substrate (2), opposite the first, a revelation frame (4) superimposed on the combined image (I), which allows to observe the encoded images (I1,. ..IN) during a change in the observation direction of the security element (1) in relation to the optical system, characterized in that the encoded images (I1 ... IN) are observable on the side of the first face and on the side of the second face of the substrate (2).

2.

Security article according to claim 1, wherein the security element (1) appears in a window (31, 32) of the security article (1).

3.

Security article according to claim 2, wherein the window (31, 32) is formed by one or more absences of material above or below the security element (1), the window (31, 32) being less partially transparent or translucent on the side of the security element (1) opposite to the absence of material.

Four.

Security article according to claim 2, wherein the window is at least partially transparent or translucent on either side of the security element (1).

5.

Security article according to claim 2, wherein the window (31) is through.

6.

Security article according to any of the preceding claims, wherein the disclosure frame (4) and / or the combined image (I) are homogeneous in appearance with the naked eye.

7.

Security article according to any of the preceding claims, wherein the revelation frame (4) and / or the combined image (I) are formed with at least two overlapping colors, the coded images being observable on the side of the first face and on the side of the second face of the substrate (2) with different colors.

8.

Security article according to any of the preceding claims, comprising an alternation of optical systems associated with two respective observation directions perpendicular to each other, in particular optical systems whose respective revealing frames have perpendicular orientations.

9.

Security article according to any of the preceding claims, wherein the security element is presented in the form of a security thread, a sheet or a patch.

10.

Security article according to any one of the preceding claims, wherein the revealing frame (4) comprises at least a first fluorescent zone capable of emitting, by a predefined lighting condition, a visible light of a first color, and a combined image (I) comprises at least a second fluorescent zone capable of emitting by fluorescence, in the condition of predefined lighting, a visible light of a second color, different from the first, being at least one of the first and second zones fluorescent, in particular the two, at least partially opaque, at least in the pre-defined lighting condition, and the first and second fluorescent zones overlapping at least partially so that, in the pre-defined lighting condition, a light passing through successively the two fluorescent zones have a third color different from the first and second colors.

eleven.

Security article according to any of the preceding claims, wherein the security element (1) comprises two frames of revelations (4a, 4b) respectively associated with two combined images (Ia, Ib), the orientation of the bands of a of the revelation frames different from that of the other disclosure frame.

12.

Security article according to any of the preceding claims, comprising a perforation (40) in which at least partially the security element (1) corresponding to the juxtaposition of two sub-elements (41, 42) is placed, in particular in form of sheets or patches, which respectively comprise the revelation frame (4) and the corresponding combined image (I).

13.

Security article according to any one of claims 1 to 11, wherein the disclosure frame (4) or the combined image (I) is made in the form of prints on the surface of the article, covering a

14 E10740387 05-09-2014 at least partially sub-element (43), in particular in the form of a sheet or patch, the impressions formed, the sub-element (43) comprising the combined image (I) or the corresponding revelation frame (4). 14. Procedure for authenticating a security article as defined in any one of claims 1 to 13, comprising the step of observing the security article by varying the observation direction and concluding on the authenticity of the article or of an object associated with the security article at least based on the encoded images observed. fifteen